While antibiotic-resistant bacteria are on the rise, you might have thought that the potentially deadly bugs would be found mostly in the places where people and other animals congregate: namely, the surface of the Earth. But researchers from Canada and France have found them in a most remarkable place.
Antimicrobial-resistant bacteria and fungi are responsible for killing at least 1.27 million people worldwide every year, according to the Centers for Disease Control and Prevention. Fighting these superbugs is getting increasingly difficult, although researchers are working on some novel methods including using gold, self-assembling "nanonets," and shape-shifting antibiotics.
Because of the significant public health threat posed by antibiotic resistant microbes, learning as much about them and how they move about our planet is critical. That's what researchers from Université Laval in Quebec, Canada and Université Clermont Auvergne in France set out to do when they investigated clouds floating around a dormant volcano in France's Massif Central region. Working out of a weather station located 1,465 meters (about 4,806 ft) high on the Puy de Dôme summit, they conducted 12 cloud-sampling sessions over the course of two years.
They not only found that the clouds contained about 8,000 bacteria per milliliter of water, but that there were, on average, 20,800 copies of antibiotic-resistant genes in the same volume. They also noted that clouds which had arrived from pathways that took them over the ocean had different kinds of antibiotic-resistant bacteria than those that passed exclusively over land – the latter had higher rates of bacteria that were resistant to antibiotics used with livestock.
While the atmosphere has long been understood as a transit point for bacteria, it was surprising to the researchers to find the same levels of the genes in clouds as they would down on the surface of the planet.
"This is the first study to show that clouds harbor antibiotic resistance genes of bacterial origin in concentrations comparable to other natural environments," says Université Laval's Florent Rossi, first author of the study. "These bacteria usually live on the surface of vegetation or soil. They are aerosolized by the wind or by human activities, and some of them rise into the atmosphere and participate in the formation of clouds."
The high concentrations of the antibiotic-resistant genes in the clouds, say the study authors, is likely primarily caused by the use of antibiotics in animal farming. Tracking the sources of the genes in future studies could help better contain the bugs, and may be a source of future research for the team.
"Our study shows that clouds are an important pathway for antibiotic-resistance genes spreading over short and long ranges," said Rossi. "Ideally, we would like to locate emission sources resulting from human activities to limit the dispersal of these genes."
The research has been published in the journal, Science of The Total Environment.
Source: Université Laval via EurekAlert